Early Out Retirements At The National Weather Service

The National Weather Service plans to offer early retirement to up to 1000 of its 4700 employees in order to cut costs. The plan, called the VoluntaryEarly Out Retirement Authority (VERA) Implementation Plan, is preliminary, and still needs approval from the Office of Personnel Management. Under the plan, 13 of the National Hurricane Center's 42 employees would be offered early retirement, and would potentially be replaced by lower-paid entry level meteorologists, in order to cut costs.

I contacted Dan Sobien, vice president of the National Weather Service Employees Organization, to ask his opinion of the plan. While he supported the idea of offering early retirement to NWS workers, he expressed concern about offering the package to operational forecasters that issue warnings. These critical people could potentially be replaced by interns straight out of college. In particular, he pointed to the part of the proposal that states:

"NWS management will determine if the vacant position needs to be filled"

Sobien remarked, "My objection is using the word "if" when talking about operational positions". He added, "Even when they agree to fill a position, they are stating that 1) they can hold it open indefinitely, and 2) they can replace a lead forecaster or journeyman forecaster with an intern."

According to the Washington Post, Greg Romano, a Weather Service spokesman, predicted that only 50 NWS employees would take the early retirement. The Post article quoted Sen. Bill Nelson (D-Fla.)--a member of the Senate Commerce, Science and Transportation Committee, which oversees the Weather Service--as saying: "They better be very careful not to cut critical jobs. I think it is wrongheaded budgetary planning, and we're going to have to try to reverse it." Nelson was particularly upset that the NWS was "unbelievably" offering early-outs to 13 of the 42 employees at the Hurricane Centerafter he had pushed Congress to add four positions to their staff to reduce the use of military personnel during hurricane season. I share these concerns, and hope the NWS amends the plans so that senior operational forecasters at the NHC and local NWS offices are offered early outs in a more intelligent fashion.

My next blog will be on Wednesday, concerning the International Environmental Data Rescue Organization. I will be travelling the for the next week, and will not be able to respond to user queries during that time.

South Atlantic tropical depression dissipates

Satellite images and wind measurements from the Quikscat satellite show that a rare tropical depression in the South Atlantic probably formed for a few hours today, but the storm has since been sheared apart by strong upper-level winds, and is not a threat to re-develop. Although the storm was tropical, had a closed circulation, and winds of up to 35 mph (according to the Quikscat satellite), it only had those characteristics for about three hours today. The National Hurricane Center usually does not designate a system as a tropical depression unless it can hold together for at least six hours. The system formed near 29S 36W, about 600 miles southeast of Rio de Janeiro, Brazil, over waters of about 27 degrees C--well above the 26 C threshold needed for tropical storm formation.

Figure 1.Visible image from 1613 GMT February 24, 2006, taken by the polar-orbiting AQUA satellite, showing a possible tropical depression that formed in the South Atlantic.

Are South Atlantic tropical cyclones a sign of climate change?Only one hurricane and two tropical depressions have been observed in the South Atlantic since 1970, when accurate tracking methods became available with the advent of weather satellites. There is usually too much wind shear to allow a tropical cyclone to form, and the South Atlantic lacks an active "Intertropical Convergence Zone" (ITCZ)--that stormy band of weather that stretches along the Equator and acts as a source region for many of the disturances that grow into Northern Atlantic hurricanes. With Hurricane Catarina of March 2004, another tropical depression in January 2004, and now yet another "near miss" tropical cyclone in the South Atlantic, I believe is it time that the NHC considered adopting a naming system. Had today's system intensified into a tropical storm, it would not have been given a name, since there is no naming system for the South Atlantic Ocean. It's quite possible that the recent activity in the South Atlantic is due to climate change causing wind shear levels to drop over the South Atlantic. The alternative explanation is that we are seeing an active period that has a long cycle, and last repeated itself before satellites were around. Given the Atlantic Multi-decadal Oscillation (AMO) that affects hurricane activity in the North Atlantic, it is reasonable to think we might see a similar pattern in the South Atlantic. In either case, it's time we had a system in place to start naming these storms to avoid confusion.

My next blog will be on Monday, a discussion of the proposed NWS staff reductions via an early retirement plan. Will we lose our best forecasters at the NHC and other NWS forecast offices?

South Atlantic tropical depression?

Satellite imagery shows what may be a rare tropical depression forming in the South Atlantic off the coast of Brazil. At 2pm EST, the system was located near 30S 35W, about 600 miles southeast of Rio de Janeiro, Brazil. The system is moving east--away from Brazil--at about 20 mph. This is a very small storm, and is not a threat to any land. The system does have a closed ciculation, but little spiral banding. It is currently over waters of about 27 degrees C, well above the 26 C threshold needed for tropical storm formation. A modest area of deep convection with quite cold cloud tops has developed in the past three hours on the southeast side of the center. Upper-level wind shear from the northwest appears to be keeping this convection from wrapping all the way around the center. The high wind shear will probably interfere with the storm's organization enough to keep a tropical depression from forming, and the system should dissipate by Saturday. The best way to track the storm is by using the visible and IR floater satellite loops.

Figure 1.Visible image from 1613 GMT February 24, 2006, taken by the polar-orbiting AQUA satellite, showing a possible tropical depression forming in the South Atlantic.

Only one hurricane and two tropical depressions have ever been observed in the South Atlantic. Satellites first began monitoring the ocean in 1970, so other tropical cyclones may have formed before that time. Tropical Cyclone Catarina, which struck Brazil's Catarina State as a Category 1 hurricane in March, 2004, was the only hurricane on record in the South Atlantic. Tropical depressions were observed in January 2004 off of the Brazilian coast, and in April 1991 off of the coast of Angola.

I'll have an update early this evening with more information. There is a pass of the Quikscat satellite coming up soon, so we should be able to get an idea of the winds of this system. It is difficult to assemble information on the storm, all of my tools are geared for the North Atlantic!

Greenland's greenhouse

Glaciers in southern Greenland are flowing 30% to 210% faster then they were ten years ago, and the overall amount of ice dumped into the sea from Greenland increased from 90 cubic km in 1996 to 224 cubic km in 2005, up 250%. As a result, Greenland's contribution to average annual sea rise increased from .23 mm/year in 1996 to .57 mm/year in 2005, and now accounts for between 20% and 38% of the observed yearly global sea level rise. Two-thirds of Greenland's contribution (.38 mm/yr) was due to glacier dynamics (chunks of ice breaking off and melting), and one-third (.19 mm/yr) from melting. These were the results of a paper called "Changes in the Velocity Structure of the Greenland Ice Sheet" published last Friday in Science magazine. NASA scientist Eric Rignot and University of Kansas researcher Pannir Kanagaratnam used ten years of satellite radar interferometry data to arrive at their conclusions.

The authors attributed the speedier glacier flow in southeast Greenland to climate warming, and noted that there had been a 3° C rise in temperature in the past 20 years at one station there. Widespread glacier acceleration affected just the southern tip of Greenland south of 66° north between 1996 and 2000, then spread rapidly northwards to 70° north by 2005 to cover the southern half of Greenland. The authors anticipated that as glacier acceleration continued to spread northward, Greenland's contribution to global sea level rise would continue to increase in coming years.

Greenland's increase in glacier speed and a corresponding rise in global sea level are reason for great concern, since Greenland holds enough ice to raise global sea level by over 20 feet (6.5 meters), should the ice cap disintegrate. However, the paper does not discuss many complicating factors, and it is uncertain if the paper's findings mean that Greenland's ice cap is in immediate danger. The most worrying aspect of the paper's findings is that we are told that the computer models used to estimate how long it will take Greenland's ice will melt are significantly in error--and in the wrong direction!

Figure 1. Change in sea level from 1993 to the end of 2004 shows a steady increase of about 3 mm/year. No acceleration of sea level rise due to increased input from Greenland or other causes is apparent. Image credit: University of Colorado.

Is the new Greenland melting evident in global sea level trends?Sea level is a surprisingly difficult thing to measure. Tide gauges are very noisy, and only show sea level trend for the coastal areas they happen to be installed on. Global sea level trends from these gauges show a rise of between 1.5 and 2.1 mm/yr for the period 1950-2000. Satellite data from the TOPEX/POSEIDON and JASON satellites can give a better global picture, and show a rise of 2.9 mm/yr for the period 1993-2004 (Figure 1). This had increased to 3.4 mm/year for the period 1993-2007. The reason for the disagreement between the tide gauges and satellite data is unknown. There is a lot of variability in the data, due to changes in evaporation and precipitation related to such events as El Niño and La Niña. Indeed, sea level is not rising everywhere. In Scandinavia, the land is still rebounding from the Ice Age, and local sea level is receding. Sea level is also not increasing in the South Pacific's Vanuatu Islands, which Michael Crichton focuses on in his State of Fear book. This lack of sea level rise is not well understood, but may in part due to regional ocean current and precipitation patterns that reduce the amount of sea level rise one might expect. Mitrovica et.al. (2001) argue that as an ice sheet melts, the gravitational pull of the ice sheet on the surrounding ocean decreases, so that a substantial melting of the Greenland ice sheet would result in substantial drop in sea level over the North Atlantic, and a major sea level rise over the South Pacific with the maximum rise near the southern part of South America.

Given how noisy the global sea level data is, it should be no surprise that an increasing trend in sea level due to the increased contribution from Greenland is not apparent in Figure 1. According to Rignot and Kanagaratnam, Greenland's contribution to global sea level rise increased from .23 mm/year in 1996 to .57 mm/year in 2005, an increase of .34 mm/year. This is less than the error bounds of .4 mm/yr in the Figure 1 satellite data. It is also worth noting that while Rignot and Kanagaratnam's estimates to contributions to sea level rise due to glacier flow (.38 mm/yr) are not disputed by other studies, their estimate of the amount of melting Greenland is undergoing (.19 mm/yr) is in dispute. For example, Box et al. (2004) came up with a global sea level rise of 1.5 mm/yr due to Greenland's contributions, and Chylek et. al. (2004) say that the ice sheet may not be adding to sea level rise at all.

Figure 2. Average temperatures for the two stations in Greenland with a century-long record. Top: Godthab. Bottom: Angmagssalik. Image credit: NASA Goddard.

Is Greenland's Ice Cap in danger of disintegrating?Greenland's ice cap is probably not in immediate danger of disintegrating, if temperatures stay at their current levels. Most of Greenland has been in a cooling trend over much of the last 60 years. It is only during the past ten years that we have seen a sharp upward jump in the temperatures at many (but not all) Greenland locations. However, temperatures as warm as Greenland is seeing now were also observed back in the Medieval Warm Period of 800-1300 A.D., and again in the 1930s. We can see the warm period of the 1930's reflected in the temperature records for two Greenland stations with records extending back over a century (Figure 2). Presumably, Greenland's glaciers at that time accelerated to speeds similar to what we are seeing today, without the ice cap suffering significant disintegration. I haven't looked for records of glacier flow and iceberg calving for that time period to check this hypothesis; I doubt reliable records exist.

Natural VariabilityThe temperature plot of Figure 2 demonstrates that Greenland is subject to large decades-long changes in its climate due to natural variation. The 2-4° C increase in temperature during the 1920s must have been primarily due to natural causes, since human-emitted greenhouse gases were relatively low then. Research results show that the climate of Greenland is dominated by a regional weather pattern called the North Atlantic Oscillation (NAO). The NAO oscillates unpredictably between a negative phase and a positive phase. If the wintertime NAO is negative, the persistent low-pressure area near Iceland called the Icelandic Low moves towards the southern tip of Greenland, bringing a sharp increase in precipitation and warmer temperatures to the island. During the positive phase of the NAO, the Icelandic Low moves back towards Iceland, allowing colder and drier conditions to prevail over Greenland. The wintertime NAO during 1950-2000 was primarily positive, which led to cooling over virtually all of Greenland--the opposite of the global warming trend of most of the rest of the world (Chylek et al., 2004). This cooling reduced the amount of glacier break-up and melting one would have expected due to global warming. To make things more complicated, increased precipitation during the wintertime negative NAO phase tends to add mass to the ice sheet in the interior, and may partially or totally offset the mass loss due to melting from that phase's increased temperatures (Johannessen, 2005). This is a very complicated system with many unknowns! The question--which was not discussed in Rignot and Kanagaratnam's paper--is, how will the expected rise in global temperatures of 1.5 to 4.5° C this century affect the NAO, and thus Greenland's temperature and precipitation? The current consensus from the computer models is that global warming should act to create a more positive NAO, which would keep Greenland cooler and drier.

When will Greenland's Ice Cap be gone?The consensus view (Gregory et. al, 2004), using computer models that treat the Greenland ice sheet as a static hunk of ice, has been that the Greenland ice sheet will melt in about a thousand years, if atmospheric CO2 doubles. However, the doubling in glacier flow observed in the past ten years comes as a major shock. The models used to come up with the 1000 year estimate do not account for changes in glacier speed at all! The unexpected increase in glacier flow probably occurred in response to the lubrication effect of melt-water penetrating down to the glacial bed, as well as other poorly-understood processes. The paper concluded: "Current models used to project the contribution to sea level from the Greenland Ice Sheet in a changing climate do not include such physical processes and hence do not account for the effect of glacier dynamics." In other words, the models were wrong. Climate change skeptics are find of criticizing computer models, and cite their inadequacy as grounds for dismissing the threat of climate change. Well, it works both ways. Climate change models can be off in the wrong direction--as we also saw with the Antarctic ozone hole, which was completely missed by the models. These new results imply that if Greenland warms significantly (at least 3° degrees C), Greenland's ice could melt in a few centuries, not 1000 years. With 20 feet of sea level rise locked up in its ice, sea level rises well beyond the capability of humans to handle could occur later this century. The real test of the stability of the Greenland Ice Sheet will come when we reach temperatures not seen since before the last ice age, 125,000 years ago. Warm temperatures then caused the Greenland Ice Sheet to mostly disintegrate, leading to perhaps 14-17 feet (4.5-5 meters) of sea level rise (Cuffey and Marshall, 2000). The likelihood of this scenario is highly uncertain, though, given our lack of understanding of the system, the high amount of natural variability, and the limited amount of historical data we have to look at.

One interesting political noteRignot works for NASA, which has recently been embroiled in controversy over whether political appointees there had tried to silence NASA climate scientist Jim Hansen from voicing his opinions. According to Time Magazine, when Rignot was asked if anyone at NASA had tried to shut him up, he said he had not been subjected to any such pressure.

Happy Birthday, Kyoto

Last week marked the one-year anniversary of the Kyoto Protocol, which went into effect on February 16, 2005. The world's industrialized countries that signed the Protocol are legally obligated to reduce their emissions of greenhouse gases such as CO2 by a total of 5.2% (compared to 1990 emissions) by 2012. The U.S. and Australia did not participate, and developing countries were not asked to. About 50% of world's emissions of greenhouse gases come from Kyoto nations, so if the treaty were successful, global emissions would fall by about 2.6%.

How are the signatory nations doing so far?Not very well, according to both critics and supporters. It seems unlikely that Kyoto's goal will be met by 2012. For example, the European Environment Agency warned in November that the European Union was likely to cut its emission by only 2.5% by 2012, not the 8% they promised under the Kyoto Protocol. It now appears that the only EU members that might meet their targeted reductions are Sweden and the UK.

Below I've tablulated recent estimates (usually from 2003 or 2004) of how the various countries are doing, percentagewise, in terms of slashing their emissions compared to the 1990 benchmark.

Non-signatory countries---------------------------------U.S. +16% (25% of world's total emissions)India +80% (5% of world's total emissions)China +46% (15% of world's total emissions)Australia +31% (2% of world's total emissions)

Britain, Germany, and the former Soviet bloc countries have made big reductions. However, their cuts have had litte to do with Kyoto. Germany and some Soviet bloc countries got big one-time savings by closing inefficient coal-fired plants in the early 1990s after the collapse of the Soviet Union. Economic hard times have also contributed to the emissions reductions in some of these countries. In the UK, electric utilities in the 1990s shifted from burning coal, which has high CO2 emissions, to cleaner-burning natural gas. Now that the price of natural gas has risen relative to coal, more UK utilities are burning coal. CO2 emissions are increasing once more, and were up over 1% in 2004 compared to 2003. The UK was slated to make a 12% cut in emissions under the Kyoto pact, and the government announced last week that this was unlikely to happen.

What can countries who are failing to meet Kyoto targets do?Under the U.N.'s "clean development mechanism," developed countries are allowed to exceed their emissions allowance by investing in emissions projects in less-developed nations, trading the emission reduction abroad for emissions output at home. It is likely that many nations will resort to this trick in the coming years in order to meet the Kyoto requirements.

What happens if a country misses its Kyoto Protocol target in 2012?Then they have to pay back at a penalty rate (130%) in the years after 2012, when there will presumably be a new agreement for the 2013-2018 period. Negotiations to hammer out a successor agreement are set to begin in May 2006 in Bonn, Germany. It is possible that countries that are failing to meet their Kyoto Protocol targets for 2012 will choose not to sign successor agreement, to avoid the penalty. Also, any nation that signed the Kyoto Protocol is allowed to drop out after three years--on February 16, 2008. Some nations may take this route to avoid the penalty.

Is Kyoto having a significant impact?The Kyoto Protocol's target of a 5.2% reduction in emissions is tiny compared to what is needed in order to prevent substantial warming. Critics say this proves the worthlessness of the treaty, while supporters say it is a neccesary first step. In order to achieve a maximum 2�C temperature rise, some studies project global CO2 cuts of 50% by 2050 are required. Industrialized countries would have to cut their CO2 emissions by 80%. Considering that the world's nations that are trying to reduce emissions via the Kyoto Protocol are unlikely to meet even a 5% reduction, it looks pretty likely that we'll be seeing a much warmer world by the end of the century.

Is there hope for avoiding a major warming this century?There is a large amount of uncertainty in both the social and scientific aspects of climate change that leave some hope that we will avoid warming the Earth by 2�C this century. I've composed a list of five possible scenarios that might cause this, and ordered them from most likely to least likely:

Dr. Jeff Masters' top five list of 21st Century scenarios that might keep us from warming 2�C this century:

1) A dramatic climate change disaster or potential disaster will suddenly unfold, spurring the nations of the world to cut emissions drastically (similar to what the emergence of the Antarctic Ozone Hole did for regulating CFCs).

2) We luck out, and climate change turns out to be at the cool end of the scientific uncertainty estimates.

3) The global economy will crash due to war, natural disaster, climate change, or other causes, bringing drastically reduced emissions.

5) Aliens will land and give us their non-polluting, limitless energy technology.

I'm hoping for scenario #4 or #5, but I think there is a significant chance scenario #1 will happen in the period 15 to 50 years from now. We may well be pushing the climate system too hard and in too many ways to avoid triggering a climate shift that will cause big trouble for a lot of people. I'll expand on the possibilities in future blogs this month.

Next blog (probably on Wednesday): A possible candidate for scenario #1: the bad news from Greenland reported last Friday in Science magazine.

Philippines disaster

Heavy rains of up to 12 inches during the past week on Leyte Island in the Philippines have triggered mudslides that have killed hundreds and left over 1,500 people missing today. As we can see from a rainfall plot of the past week's rainfall (Figure 1), these heavy rains have affected only a small portion of the Philippines, and the rest of the Islands have escaped major rains. A modest La Ni�a episode is affecting the Pacific Ocean this winter, and precipitation over the Philippines is typically enhanced during a La Ni�a episode. We should not be surprised to hear of further heavy rain problems in the Philippines, Indonesia, and northern Australia over the coming months, unfortunately, due to the presence of La Ni�a. All of these regions usually experience above-normal rains during a La Ni�a episode.

Figure 1. Precipitation for the week ending February 17, 2006, as observed by the NASA TRMM satellite.

Flying into a record Nor'easter

Blizzard of 2006: a Category 3 stormBefore we talk about flying into one of the most severe Nor'easters of all time, lets mention the Blizzard of 2006 once more. NOAA has classified the storm as a Category 3 storm on the new NESIS storm scale, two notches down from the most severe kind of blizzard. While the Blizzard of 2006 set snowfall records in New York City and Hartford, the overall size of the area affected was lower than in mega-blizzards like the Superstorm of 1993 that earned Category 5 rankings.

Tale of a record-breaking Nor'easterIf you're wondering what the NOAA Hurricane Hunters do in the winter when they're not flying hurricanes, the answer is simple--they're somewhere else where the weather is bad! During my four years with the Hurricane Hunters, I regularly spent my summers in the tropics and winters in the Arctic. I logged over 25 missions into intense winter storms as part of field projects based in Norway, Alaska, and the U.S. During the winter of 1989, we were stationed at Brunswick, Maine for three months as part of the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA). This project utilized the two NOAA P-3 research aircraft and the another aircraft with Doppler radar, the NCAR Electra, to provide an unparalleled data set documenting the life cycle of ten North Atlantic extratropical cyclones. During one of these flights, we caught the central Atlantic's most intense winter storm on record.

Figure 1. The ground crew de-ices NOAA's P-3 winter storm hunter aircraft in preparation for chasing a Nor'easter that buried the Brunswick, Maine operations base with a foot of snow.

On January 3, 1989, a strong extratropical cyclone moved off the coast of North Carolina, and pulled a large mass of Arctic air over the ocean behind it. As the cyclone crossed the warm waters of the Gulf Stream, where water temperatures were over 70 degrees, the storm "bombed". It's central pressure fell 66 mb in 18 hours to an astounding 936 mb--a pressure typical of a Category 3 or 4 hurricane! Post-analysis of the data suggested that the pressure fell even further, to 928 mb. This was the lowest pressure ever observed in an Atlantic extratropical cyclone south of 40 degrees latitude in the 20th century. But since the storm never affected land, few people outside of the research community have ever heard of it, and it doesn't even get a ranking on the NESIS scale.

I was tasked to be flight director on the daytime January 4 mission into this storm, dubbed Intensive Operating Period 4 (IOP 4). As I drove to work that morning on treacherously icy roads, I reflected on the fact that this part of my day would probably the most dangerous part--not this afternoon's flight at low altitude into a hurricane-strength winter storm! Although I had had a few rough flights on my 20 or so missions into winter storms, none had ever compared to flying into a hurricane. There isn't much deep convection in a winter storm out over the ocean, since the water is usually too cold to support intense thunderstorms. Deep convection creates sudden updraft and downdrafts--the kind of turbulence that is a bane to aircraft.

At our pre-flight briefing, though, I began to wonder if maybe the most dangerous part of the day lay ahead! The flight crew from the just-returned midnight flight reported that the storm was entering a rapid deepening cycle. They encountered intense lightning and moderate turbulence in some of the rain bands. The morning satellite imagery confirmed that we were dealing with a true monster--none of us could ever remember seeing such huge storm over the Atlantic.

We took off and droned southeastwards towards the storm. As we neared the storm, we noticed that it's far-flung rain and snow bands painted our radar displays with bright patches of color we were unused to seeing in a winter storm. The nose radar, which had a special algorithm to plot turbulent areas in a bright purple color, was showing the the first purple I had ever seen in an extratropical cyclone. As we approached the north side, we descended to 350 meters (1150 feet) in altitude and prepared to penetrate the center of the storm.

"SET CONDITION ONE!" crackled pilot Ron Phillipsborn's voice over the aircraft's loudspeakers and intercom. When announced by the Aircraft Commander, Condition One requires all hands to return to their seats and prepare for turbulence. Throughout the airplane, the crew stashed away flight bags, clip boards, and other loose items that could turn into dangerous missiles in severe turbulence, and buckled up their heavy-duty seat belts.

We plowed through an intense band of snow and rain that rocked the aircraft. The winds jumped to 60 mph. Glimpses of the ocean below revealed a maelstrom of white-capped, wind-whipped 20-foot waves.

"Whoa, that was a pretty intense band!" I remarked over the intercom as we emerged from the band and the turbulence subsided. "Ron, are you happy at 1200 feet?" I asked the pilot, who had just joined the Hurricane Hunters, and had yet to fly a mission into a hurricane.

"No problem!" Ron replied. He held us on course for a penetration straight through the center of the cyclone. When we reached the calm center, there was no spectacular view like one sees in a hurricane--the center of this storm was surrounded by clouds. But there was plenty of excitement among the science team, headed by Dr. Mel Shapiro of NOAA.

"Did you see that pressure?" Mel exclaimed. "941 millibars! And what a temperature jump--we've got an incredible amount of warm air at the core of this storm. And check out out those SST's--70 degree water. No wonder we're seeing such impressive convection!" Indeed, the radars showed an impressive amount of intense echoes on all sides of us.

We continued southward, then cut across the cold front. As we crossed the cold front, we hit a remarkable updraft of 7.5 m/s (17 mph). All around us, huge cumulonimbus clouds pushed upwards by the tremendous lift along the front lit up with impressive lightning displays. As we crashed through the front, the surface winds picked up to 100 mph, and some hard, jolting bumps of turbulence rocked the airplane. This was like flying through a Category 2 hurricane! An awesome parade of 35-foot high waves whipped into a green-white froth rolled beneath us.

"Hey Ron!" I exclaimed as we emerged into the clear beyond the cold front. "How does it feel to fly through a Category 2 hurricane?"

"No problem!" Ron replied. He was handling the turbulence like a veteran.

We turned back towards the center again. It was time to take another reading of the storm's central pressure to see how much it had deepened. As we approached the center, once more we encountered bands of showers with strong turbulence. This storm was getting to be a bit of a pain! Finally, we punched into the center again.

"Whoo-eee!" I exclaimed, as winds went calm and the lowest pressure flashed onto the monitors. "936 millibars! That's got to be a record!"

"Fantastic!" agreed Mel. "Let's go check out the triple point now." The triple point is where an extratropical cyclone's cold front, warm front, and occluded front all meet, and is often the most turbulent portion of the storm.

We turned east towards the triple point, and our ride steadily grew rougher and rougher. Frequent intense bands of showers rocked the aircraft, and the ominous purple color of turbulence grew more and more concentrated on the nose radar. Ron did his best to sneak through gaps in the clouds to avoid the worst of the turbulence, but it was still a rough, uncomfortable ride. Finally, the radar showed no more soft spots--we were surrounded on three sides by thunderstorm cells showing some very nasty-looking purple radar echoes.

"Uh, Jeff, what do you think we should do here?" Ron asked, sounding uneasy about the mass of purple directly in front of us.

I took a moment to study the radar display before replying. "Let's get out of here! U-turn, back the way we came!"

"Ron, Jeff, I think its time to do some high-altitude work!" agreed Mel. We were more than happy to oblige, and climbed to 18,000 feet to study the upper-level structure of the cyclone for a while.

PostscriptThe January 4, 1989 flight into the IOP 4 storm marked the only flight I'd ever been on where we performed a U-turn to escape severe turbulence. Despite not directly measuring the most interesting part of the storm, we were able to capture the best data set ever of an extratropical cyclone tapping the warm waters of the Gulf Stream to become a hybrid warm-core system.

Blizzicanes

Did the Blizzard of 2006 have hurricane-like characteristics? Yes, it did. To explore this more fully, let's look at the two basic types of large scale (synoptic-scale) storms that meteorologists define:

1) Tropical cyclones (hurricanes), which have a warm core, and derive their energy from the latent heat of condensation. When water vapor condenses into rain, the phase change from gas to liquid liberates some extra heat energy--the latent heat--that was used to evaporate the water in the first place. Since maximum evaporation in the atmosphere occurs over the warmest ocean waters, tropical cyclones thrive in the late summer when ocean temperatures are at their peak.

2) Extratropical cyclones (mid-latitude cyclones), which have a cold core, and derive their energy from the potential energy released when cold air aloft sinks and is replaced by warmer, less dense air. Extratropical cyclones develop where two air masses of sharply different densities (and thus, temperatures) intersect. Extratropical cyclones exist only outside of the tropics (thus are "extra"-tropical), where there is some cold air to be found. The ordinary low pressure systems that bring rain and snow to residents of the mid-latitudes are examples of extratropical cyclones.

In recent years, meteorologists have begun to discover that many extratropical cyclones--including Nor'easters, which are strong wintertime extratropical cyclones that affect the Northeast U.S.--can make a partial transition to a warm-core system once they move out over the warm waters of the Gulf Stream. Like a hurricane, deep convection will appear near the center of the storm, and the hybrid system will begin to draw energy from the latent heat of condensation. These storms can "bomb" and deepen at rates of 10 mb/hour, and reach central pressures normally associated only with major hurricanes.

Figure 1. The Blizzard of 2006, visible satellite image from NOAA for Sunday February 12 2006. Note the eye-like feature south of Rhode Island. The "eye" was near the edge of the Gulf Stream, where water temperatures increased sharply from 6 degrees to 12 degrees C.

According to Louis Uccellini and Mel Shapiro, extratropical cyclone experts with NOAA, these storms may be undergoing a "seclusion" process that creates an semi-isolated tropical system in the midst of an extratropical cyclone. In the seclusion process, a strong extratropical cyclone draws in warm air from the south, and latent heat of condensation from the cyclone's intense precipitation makes this air even warmer. This extra-warm air spirals into the center of the low and wraps around to the west side, where it is pinched off. As result, one has an isolated "warm core" center where deep convection builds and spiral banding can occur. However, unlike a hurricane, there is no eyewall, and no cloud-free eye created by sinking air (subsidence) in the center. The eye-like feature in an extratropical cyclone has upward moving air, and is merely the center where the surface winds spiral into. Spiral bands of convection can develop in the warm air near the center, mimicking the spiral bands of a hurricane. If these convective bands become intense, subsiding air on the flanks of the bands may create subsidence that warms and dries out the surrounding air, creating cloud-free regions near the center that may give it a more eye-like appearance. Another difference with hurricanes is that the upper-level high pressure system (anticyclone) over the extratropical cyclone is displaced to the northeast (downwind) of the center. In a hurricane, the anticyclone is directly over the eye.

The Blizzard of 2006 developed a distinct eye-like feature when it moved offshore over the warm Gulf Stream waters. The storm was undoubtedly tapping the hurricane's source of energy--latent heat of condensation--at the time the photo in Figure 1 was taken, since we can see evidence of spiral banding occurring neat the center of the storm. As seen in Figure 2, the Sea Surface Temperatures increased sharply from 6 to 12 degrees C (43 to 54 degrees F) near where this eye-like feature developed, right along the edge of the Gulf Stream current. There was plenty of water warm water for the storm to tap into for an extra energy source.

However, the storm missed the warmest waters of the Gulf Stream to its south, and did not intensify much compared to other historic blizzards--the storm's central pressure only dropped to about 980 mb, and a pressure of 960 mb is more typical of a classic Nor'easter "bomb". Also, note that the band of heavy snow that extends from Long Island through Connecticut northeastwards is well away from the center of the cyclone. This band is what gave the Blizzard of 2006 its prodigious snow amounts, and the band developed just as the storm moved off the coast--well before the warm ocean waters had time to create a warm-core seclusion in the storm and enhance the storm's snowfall. This band of heavy snow was created by processes unrelated to the formation of a warm core in the cyclone. The band had some similarities to the intense bands of lake-effect snow one finds in the lee of the Great Lakes--drier, fluffier snow than one usually finds in a Nor'easter, and very high snowfall rates of up to four inches per hour. Lake effect snow bands, and the extreme snow band of the Blizzard of 2006, are examples of developments on the "mesoscale"--the scale of a few tens of kilometers--and are not well handled by computer forecast models. These models typically chop the atmosphere into grid cells between 20 km and 40 km square, and thus were not able to resolve features like the extreme snow band of the Blizzard of 2006, which concentrated its heavy snow into a band just 10 or 20 kilometers wide.

Figure 2. Sea Surface Temperatures at the time of the Blizzard of 2006.

From the Sea Surface Temperature plot in Figure 2, we can see that much warmer water lies further south, along the North Carolina coast. The Gulf Stream moves parallel to the coast here. The Blizzard of 2006 missed tracking over this warmer water, since the storm popped off the coast near New Jersey then tracked due east. Thus if a winter storm crossing the U.S. can take a track so that it moves offshore near the Carolinas, then move northeastwards along the axis of the Gulf Steam, it will spend a longer time over much warmer waters than the Blizzard of 2006 did, and have chance to really tap into that latent heat of condensation energy that powers hurricanes. This is what happened to a January 1989 cyclone I flew into as part of a field project the Hurricane Hunters were participating in, called the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA). This storm "bombed" while we flew through it, the pressure dropping an astounding 60 mb in 24 hours, bottoming out at 938 mb. I'll have the tale of the rough ride through that storm later this week.

Blizzard of 2006: One for the record books

The Blizzard of 2006 is over, but not before dumping an all-time record amount of snow on New York City, 26.9 inches. This bested the total from the infamous "Great White Hurricane" of 1888 (21 inches), and the previous all-time record, 26.4", set December 26-27, 1947. The 26.9 inches at Central Park was the most snow of any location in New York State. Hartford, CT also set its all-time record for snowfall, with 21.9 inches. The previous record was 21 inches on February 11-12, 1983. The western suburbs of Hartford received as much as 27 inches. Snowfall amounts as high as 21 inches were reported in Maryland, eastern Pennsylvania and New Jersey, while Massachusetts saw up to 22 inches, New Hampshire, 17 inches, Rhode Island, 16 inches, and Maine, 13 inches. Boston received 17.5 inches and a 2.5 foot storm surge, which caused some minor flooding problems. The storm was Boston's 11th biggest snow on record.

What appeared to be a rather ordinary Nor'easter on the computer model forecasts Saturday, intensified dramatically on Sunday as the center moved out over the warm waters of the Gulf Stream. For reasons we don't understand very well, the blizzard formed an intense band of thunderstorms with snowfall rates of 2 to 4 inches per hour that swept across New York City and much of southern New England. Eleven inches of snow fell in three hours at Central Park between 7am and 10am on Sunday, the kind of "snowburst" one seldom sees except in lake-effect storms in the lee of the Great Lakes. New York City reported lightning and thunder for six hours during the height of the blizzard. Check out this 3-hour radar animation from the New York City radar Sunday morning. You can see a narrow band of extremely heavy snow that stretches from northern New Jersey through New York City and northeastward to Hartford Connecticut. This band has echo intensities of 40 dBZ, which are common in warm-season thunderstorms, but rarely observed in winter storms.

In Florida this morning, the cold air that pushed in behind the Blizzard of 2006 brought a hard freeze to most of the northern portion of the state, and freeze warnings are posted for as far south as Miami tonight. The Miami Herald reported that on Sunday over 50 people lined up outside the Burlington Coat Factory at a local mall, and thronged the cash registers 15 deep to purchase wool coats once the store opened. While winter will ease up in Florida later this week, the general winter pattern for the rest of February looks to be typical for February, with normal or below-normal temperatures for much of the U.S.

When is a blizzard like a hurricane?The Blizzard of 2006 had a distinct eye-like feature when it moved offshore over the warm Gulf of Mexico waters and intensified Sunday. Was it exhibiting hurricane-like characteristics? I'll report tomorrow on a study I participated in back in 1987 when we flew our Hurricane Hunter airplanes through one of the strongest Nor'easters ever recorded, to help answer this question.

Historic blizzard pounds NYC

The blizzard of 2006 has dropped the most snow ever on New York City, a record 26.9 inches as of 4:10 pm at Central Park. The previous biggest snowstorm of all time was 26.4", set Dec 26-27 1947. What appeared to be a rather ordinary Nor'easter on the computer model forecasts yesterday--one that I thought would turn out to be a Category 2 snowstorm on the newly-launched NESIS storm scale for Northeast U.S. snowstorms--has intensified dramatically this morning, and will probably end up ranked as a Category 4 storm on the NESIS scale. As of 7am, Central Park recorded 12 inches of new snow--before an intense mesoscale band of snow with snowfall rates of 2 to 4 inches per hour swept through the city, bringing visibility to zero at LaGuardia Airport. Eleven inches of snow fell in three hours at Central Park between 7am and 10am. This intense band of snow, called a "snowburst", is a result of very unstable air that has organized into thunderstorms. Reports of lightning and thunder have been common today all across the Northeast in association with these snowbursts. Check out this 3-hour radar animation from the New York City radar this morning. You can see a narrow band of extremely heavy snow that stretches from northern New Jersey through New York City and northeastward to Hartford Connecticut. This band has echo intensities of 40 dBZ, which are commmon in warm-season thunderstorms, but seldom observed in winter storms. This narrow band of snow is gradually progressing eastward, and will bring exceptionally heavy snows to Long Island, Connecticut, Rhode Island, and Massachusetts today. Snow amounts of 16-24 inches will be common across New York, New Jersey, Maryland, Eastern Pennsylvania, Connecticut, and Rhode Island today.

Over in Massachusetts, the Blizzard of 2006 is expected to cause moderate flooding problems, but nowhere near the scale of the famous Blizzard of 1978. While the blizzard of 2006 is a prodigious snow-producer, its central pressure is not as low as the Blizzard of 1978, and thus its winds are much weaker. The Blizzard of 1978 had sustained winds of 65 mph, while the Blizzard of 2006 can only boast sustained 45 mph winds. The combination of storm tides of 12 feet at Boston Harbor combined with seas between 16 and 22 feet at the time of high tide may produce some structural damage to roads, sea walls, and vulnerable coastal structures around the time of high tide late this morning and early afternoon along the Massachusetts coast.

Down in Florida, the Arctic air mass associated with the Blizzard of 2006 has pushed a strong cold front through the state, bringing the threat of a hard freeze to Florida's citrus groves tonight. Snow flurries are not out of the question in northern Florida tonight and early Monday morning as a weak upper-level disturbance moves through the area. After a long holiday in January, winter has stormed back with a vengance across the eastern half of the U.S.!

Global warming underestimated?

Are the official estimates of a 1.4° to 5.8°C (2.5° to 10.4°F) increase in global mean surface temperatures by the year 2100 significantly in error? That was the conclusion of MIT professor Dr. Peter H. Stone, in a lecture I attended last week at the annual meeting of the American Meteorological Society. Dr. Stone's results were also published January 13, 2006 in Geophysical Research Letters. The "official word" in the science of climate change comes from the United Nations-sponsored Intergovernmental Panel on Climate Change (IPCC), a collaborative effort between over 2,000 scientists from over 100 countries, including many of the top climate researchers in the U.S. The IPCC publishes an extensive assessment of the state of the science every six years. The most recent report, issued in 2001, predicted the 1.4° to 5.8°C increase. If Dr. Stone is right, the next IPCC assessment, due out in 2007, will have to revise that estimate upwards.

Dr. Stone started his talk by posting this quote from the Executive Summary of the 2001 IPCC model evaluation chapter: "Confidence in the ability of models to project future climates is increased by the ability of several models to reproduce the warming trend in 20th century surface air temperature when driven by radiative forcing due to increasing greenhouse gases and sulphate aerosols." (The term "forcing" in climate research refers to any process, natural or human-caused, that "forces" the climate to respond in a significant way.) The IPCC report supported their statement by comparing climate simulations of the observed 20th century climate that used just natural processes ("forcings" such as volcanic eruptions and natural changes in the sun's brightness) with simulations done including human-caused "forcings" (greenhouse-effect gases added since pre-industrial times, plus aerosol particle pollution). Dr. Stone presented Figure 4 (below), a modified version of a figure from the 2001 IPCC report. The figure shows a typical 20th century climate simulation by one of the major climate models used for the IPCC assessment--the UK Hadley Center model. The results look good. The model is able to reproduce the observed climate of the 20th century. In addition, the simulation shows that one cannot explain the observed 20th century global warming of 0.6°C without including human-caused (anthropogenic) climate forcings.

Dr. Stone argued that the IPCC's confidence in the ability of models such as the UK Hadley Center Model to predict future climate was invalid, and that the good agreement between the observed climate and model prediction seen in the figure above could have been coincidence. He outlined several ways that compensating errors in two or more areas of model uncertainty could have produced a climate simulation that matched the observed 20th century record.

Major uncertainties in climate change computer models include:

1) Climate Sensitivity (how much global surface temperature changes when CO2 is doubled)2) Rate at which the oceans take up heat3) Strength of forcing by aerosol particles4) Natural variability

For example, if a model has a Climate Sensitivity that is too great (the model predicts too much warming for a given increase in CO2), and improperly assumes too much cooling will occur due to pollution from aerosol particles, the two errors will cancel each other out and lead to a realistic-looking simulation. The Climate Sensitivities of the 11 key models used to generate the 2001 IPCC results varied by about a factor of 2.5, from 1.5°C to 4.5°C. Similarly, the amount of heat taken up by oceans varied by about a factor of 2.5 in the models. Additional uncertainties exist in the models' treatment of aerosols and natural variability.

Rather than dismiss the climate models as being too filled with uncertainty to be useful for performing climate simulations, Dr. Stone maintained that one can do an intelligent uncertainty analysis by varying two of the major uncertainties in a model simultaneously, and study the resulting model predictions. He described his group's research to evaluate the uncertainties in 11 of the key models used to formulate the 2001 IPCC climate report. The study was done using data from the Coupled Model Intercomparison Project (CMIP), an international research program begun in 1995. The talk then became quite technical, with several plots showing Probability Distribution Functions on parameter-space diagrams. It was at this point I bemusedly watched the audience member next to me who hadn't had enough cappuccino that morning repeat the classic pecking bird "doze-droop-jerk-I'm awake!" pattern. Meteorology talks aren't always filled with captivating displays of 3-D Category 5 hurricanes! There's a lot of hard science needed to understand the concepts.

Finally, Dr. Stone finished his uncertainty analysis, and he presented some rather startling conclusions:

1) Models have been over-estimating the rate of mixing of heat into the deep ocean.

2) This implies that their projections of surface warming for the 21st century are too low.

The guy next to me jerked fully awake now, and the audience got noticeably more attentive. "And this worries me," Dr, Stone continued. "It worries me enough that we've made many extensive tests of our methodology that try to make sure that there are no flaws. I would be delighted if anybody here could come up with a test that we might look at to see if we've done anything wrong." The audience, filled with several hundred people, including many of the world's foremost climate experts, was silent. No one could come up with a reason to dispute Dr. Stone's gloomy conclusion.

So how much in error are the climate models? Dr. Stone didn't give a number in his talk, and when I asked him about this later he said he had only a rough preliminary idea of what this error might be. His research team is currently analyzing their results to see how much additional warming we can expect. When they publish some specific error estimates, I'll be sure to post a follow-up blog on the subject.

Professor Stone's talk can be heard on-line for free. To do so, you must install the free WebEx player for IE or Netscape. Note: this will not work for other browsers, such as Firefox! The talk is about 40 minutes long, and includes figures. Alternatively, you can read the paper on the subject that he co-authored along with C.E. Forest and A.P. Sokolov of MIT's Joint Program on the Science and Policy of Global Change:

A free abstract of the paper is available from the agu.org website. A full version costs $9 for non-subscribers.

A note on my global warming blogsIn an issue as complex, contentious, and important as global warming, it is impossible for anyone to present an unbiased and fair treatment of the subject. My bias will be towards presenting new scientific findings published in peer-reviewed journals, as well as calling attention to the political aspects of the debate when it appears that one side or the other is attempting to twist or hide the truth. While thus far I have only focused on the NASA/Dr. James Hansen affair, I also have criticism of those claim that Hurricane Katrina was significantly enhanced by global warming. Although it is possible that global warming did contribute significantly to Katrina's intensity, the current best hurricane science supports only a 1-2 mph enhancement in Katrina's winds by global warming. I have a blog on this topic I plan to post next week, highlighting recent questionable statements by the editor of Science magazine on the matter.

For those of you following the NASA/Dr. James Hansen affair, see this morning's New York Times article, where George C. Deutsch, the young NASA press aide who resigned on Tuesday amid claims that he had tried to keep Dr. James Hansen from speaking publicly about global warming, defends himself publicly.

A note on media bias on the global warming issueI'm of the opinion that articles in the New York Times on global warming tend to be biased in favor of dramatizing the problem and calling for action. Articles in the Wall Street Journal, Washington Times, and Newsweek magazine generally have the opposite bias. Time magazine seems pretty neutral, and CNN.com may have a pro-action bias. I'm not sure about the USA Today, Washington Post, or other sources. One of my favorite sources of global warming info (but a little too technical for many readers) is from realclimate.org, which is maintained by some of the top climate scientists in the field. They have serious disagreements with the Wall Street Journal.

No Alberto, and the NASA/Dr. James Hansen affair

Watching for AlbertoThere will be no Subtropical Storm Alberto forming from the large cold-cored low pressure system off of the coast of Africa today. There has been no increase in deep convection near the storm's center the past 24 hours, and the storm has stayed over chilly waters less than 20 degrees C. The Greek tropical cyclones of 2005 that formed in a location similar to that of today's storm--Delta, Epsilon, and Zeta--all had ocean temperatures of at least 22 C to work with. It appears that 20 C is just too cold to support a tropical or sub-tropical system in this region. Today's storm--which does have winds of 35 mph, just below tropical storm force--is forecast to remain over waters cooler than 20 C and weaken as it slides slowly southeastward towards the African coast over the next few days.

Figure 1. Visible satellite image from 1300 GMT February 9, 2006, shows no sign of increased convection associated with the large low pressure system off of the coast of Africa. Image credit: Naval Research Lab, Monterey.

More on the NASA/Dr. James Hansen affairAs I reported in a blog two weeks ago: NASA tries to silence its top climate researcher, political appointees at NASA and NOAA have recently been attempting to control the flow of information coming out of the agencies. There are two more New York Times stories that have come out on the affair. Yesterday's story reports on the resignation of George C. Deutsch, the young presidential appointee at NASA who told public affairs workers to limit reporters' access to Dr. James Hansen, NASA's top climate researcher. Apparently Mr. Deutsch had falsified his resume, claiming to have graduated from college, when transcripts revealed that was not the case. The second article, published February 4, reports that NASA's top administrator, Michael D. Griffin, issued a sharply worded statement calling for "scientific openness" throughout the agency. It sounds like for now, there will be less restriction on information coming out of NASA, which is a welcome change.

Warmest January on record in U.S.

As expected, January 2006 was by far the warmest January in the U.S. since record keeping began in 1895. According to data released by the National Climatic Data Center yesterday, the country's average temperature for the month was 39.5 degrees Fahrenheit, 8.5 degrees above average, and a full 2.2 degrees above the old record of 37.3 degrees set in January 1953. The 3-month period November through January was the third warmest such 3-month period on record. Temperatures over the past 6 months (August-January) were the warmest on record, and temperatures for the past year (February - January) were the fifth warmest on record.

Every state recorded above average temperatures, and 15 states recorded their warmest January ever (Figure 1). Temperatures between 15 and 20 degrees above normal were common across much of the northern Plains (Figure 2), and only a few small pockets in the Western states saw below normal temperatures.

Figure 1. How each state ranked in terms of record warm temperatures for January 2006. A rank of 112 means it was the warmest January on record for the past 112 years.

Figure 2. Temperature departure from normal for January 2006.

Precipitation for January 2006 was above average, ranking 29th wettest (Figure 3). However, regions of Texas, Oklahoma, New Mexico, and surrounding states had much below precipitation, contributing to severe drought conditions. Phoenix, Arizona, has not had precipitation since October 18--a stretch of 113 days--breaking its old record for longest dry stretch, 101 days in 1993. There's no rain in sight for Arizona, and the current La Nina pattern is likely to bring below normal precipitation and above normal temperatures to the region for the next few months. Current dryness levels in Arizona forests are typical of those in late July, and we can expect one of Arizona's worst fire seasons on record this year.

Residents of Arizona may want to consider moving to Olympia, Washington, which set a new record for the most consecutive days with precipitation--35 (their old record was 31 days in 1953). Washington had its 2nd wettest January ever.

Figure 3. Precipitation departure from normal for January 2006.

January statistics for the rest of the globe will not be available until late next week. I'll report then on whether January 2006 was the warmest month on record globally, as well. Given the severe cold seen in Asia, I'd be surprised.

Alberto watchA large cold-cored non-tropical low pressure system spinning off the coast of Africa near the Canary Islands has gained a bit of deep convection over the past 24 hours, and has about a 10% chance of becoming Subtropical Storm Alberto in the next few days. Waters temperatures are a cool 20 - 22 C over the region, and the low is forecast to drift towards the coast of Africa and gradually dissipate by the end of the week.

Category 5 snowstorms

Hurricanes have their Category 1 - 5 rankings on the Saffir-Simpson Scale. Tornadoes are ranked F1 - F5 on the Fujita scale. Now winter storms have a similar ranking system, at least if you live in the Northeastern U.S. urban corridor. The new scale, announced last week at the annual meeting of the American Meteorological Society, is called the NESIS scale, or Northeast Snowfall Impact Scale. The NESIS scale ranks snowstorms that dump at least ten inches of snow on the Northeast U.S., with a number one to five. The five categories are Extreme, Crippling, Major, Significant, and Notable. The NESIS scale differs from the hurricane and tornado ranking scales in that it uses the number of people affected to assign its ranking. Thus, a massive blizzard that whips Massachusetts, New Hampshire, and Maine with hurricane-force winds and three feet of snow--but affects no other portions of the country--would receive a Category 1 ranking on the NESIS scale, since it only affects a small number of people. The same storm tracking up the East Coast and affecting 65 million people would receive a NESIS ranking of five. There have been only two Category 5 snowstorms to hit the Northeast U.S. the past 50 years--the blizzard of March 13, 1993, and the blizzard of January 7, 1996 (Table 2). According to the scale's creators, the scale can help the emergency managers and the public make appropriate decisions to protect lives and property, assist with evaluatation of building codes, and provide a historical perspective. The scale was developed specifically for the Northeast U.S. because of the great impact winter storms there have on the U.S. economy and transportation system.

It remains to be seen if the NESIS scale will catch on and prove useful. For me, a storm ranking scale makes sense, but trying to forecast if a northeast snowstorm will be a Category 2 or 4 will be difficult, since I'll have to keep in my head a map of the Northeast population, and try and integrate in my head what total area is likely to be covered by how much snow. This is a lot harder than looking at the wind speed and assigning a category, like is done with hurricanes. Thus, I expect it will be some time before the NESIS scale catches on, but it eventually probably will as people become used to it. There are currently no plans to extend the scale to other parts of the world.

So far this winter, there haven't been many winter storms worthy of a ranking on the NESIS scale. The snowstorm of December 9, 2005, which dumped more than a foot of snow in the Boston area, was probably a NESIS Category 2 storm. The long range winter outlook doesn't show any major Northeast snowstorms in the offing for the next week, just plenty of seasonable cold air.

Super Sunday weather bandwidth

Weather enthusiasts like to watch the Super Bowl--that's my not-so startling conclusion after analyzing the Internet bandwidth curves from the wunderground.com website from last night. In a pattern I've seen during every Super Bowl since wunderground.com opened shop in 1995, our bandwidth plot (Figure 1) shows a clear drop-off in traffic in the 45 minutes prior to the game, a sudden spike in traffic at halftime, a sharp drop when halftime ends, and a return to normal levels at the end of the game. Interestingly, the national championship game for college football has never been apparent on our bandwidth curves. The only other non-weather related event I've seen affect our bandwidth occurred in the aftermath of the 9/11 disaster when our traffic dropped below 50% of normal after 9am and stayed at less than half of normal all day.

Our sharpest spike in bandwidth due to a non-hurricane weather event occurred in 1999 when an F5 tornado ripped through Oklahoma City. Major hurricanes hitting the U.S. regularly cause large bandwidth spikes, particularly in the 30-minute period after NHC issues the 11am advisory. Our busiest day ever was September 22, 2005, as Hurricane Rita approached the Texas/Louisiana coast. Each NHC advisory issued that day created a large bandwidth spike bigger than the Super Bowl halftime spike. Google has a page showing their top searched-for natural disasters of 2005. Hurricanes Katrina and Rita produced roughly equivalent peaks, but Katrina's peak lasted much longer.

Figure 1. Plot of total bandwidth in bits/sec for a portion of the weather imagery sent out by the wunderground.com web site during the Super Bowl on February 5, 2006. The times on the bottom axis are EST.

New Orleans tornado and tropical update

While the groundhogs slumbered before their big prognosticating efforts Groundhog Day morning, two tornadoes ripped through the New Orleans metro area, adding to the misery and fright of a city still deeply wounded by the devastation of Hurricane Katrina. One tornado hit Armstrong International Airport. Here's the official NWS damage report from that event:

Weather observer observed funnel cloud at the same time that substantial damage occurred to Concourse C. 20 x 8 foot glass window along with metal frame were sucked out in walkway area just past security checkpoint. Four jet bridges were damaged. Section of temporary roof was blown away. The airport reported a peak wind gust of 43 mph at 236 am. Warehouse building reported damaged across the highway from airport.

Two other tornadoes were reported nearby. Here's the official damage reports from those events:

Ground survey indicated tornado touched down initially along River Road at Iris Ave near Oschner Hospital. Several structures had roofs removed. Warehouses damaged and power lines/poles snapped. The tornado traveled north northeast for approximately 0.75 miles. Damage width 150 yds.Several trailers near Oschner Hospital in Metairie, Jefferson Parish, sustained roof damage...roofs were torn upwards from their base.

Ground survey indicated strong tornado moved on a north northeast path across the Lakeview area of New Orleans. Several houses heavy damaged...other houses with lighter damage and power poles snapped. Former State Police troop B communications tower was knocked down on Veterans Blvd near Fleur de Lis. Damage path approximately 2.5 miles. Width approximately 150 yards. Further ground survey and investigation may result in consolidating Lakeview tornado with tornado near Oschner Hospital.

While the damage from these tornadoes will probably amount to just a few million dollars, their psychological toll will no doubt be high. At a lecture Tuesday at the American Meterological Society Annual Meeting, Dr. Anna Marie of the Weather Channel presented a talk titled, "Health Effects of 2005 Hurricanes". She presented results of a study that showed that 40% of the population of New Orleans was suffering from post-traumatic stress disorder. This is much higher than the 25 - 28% rate reported for the victims of Hurricane Andrew. A study of the psychological state of 2000 Katrina victims is being performed by the Harvard Medical School, and an update of their condition is due to be released in late February.

Are Category 4 and 5 hurrricanes increasing in frequency?I heard the authors of the paper claiming this connection speak Tuesday at the American Meteorological Society conference, and they presented new evidence supporting their conclusion. However, Dr. Chris Landsea of the National Hurricane Center presented evidence disputing their conclusions. It will take me at least a week to incorporate the new material into the blog piece I'm working on about this, pardon the delay!

Five more weeks of winter?

Punxsutawney Phil, the fearless rodent prognosticator of Punxsutawney, Pennsylvania, saw his shadow this morning. According to tradition, we can expect six more weeks of winter are on tap for the United States.

Your fearful human forecaster predicts about five more weeks of winter--including some very harsh winter weather in mid-February. This forecast is based on long range model forecasts from the GFS model, plus observations of a "resonance" in Earth's climate system called the North Atlantic Oscillation (NAO) that I discussed two weeks ago. The NAO has just switched from its positive phase to its negative phase. The negative phase is typically associated with a jet stream pattern that brings cold Arctic air to the Eastern U.S., and that is the pattern we saw in the five week period from November 16 - December 23, when cold air gripped much of the Eastern U.S. The positive phase of the NAO is associated with a northward retreat of the jet stream into Canada, and usually brings much above normal temperatures to the eastern half of the U.S. The positive phase of the NAO dominted during the five-week period from December 23 - February 2, and record warm winter conditions were experienced across most of the U.S. during these past five weeks.

Figure 1. The North Atlantic Oscillation for Nov. 1 2005 - Feb. 2, 2006. The postive phase of the NAO has been associated with warmer than average temperatures at Detroit and most of the eastern half of the U.S., while the negative phase has been associated with cooler than average temperatures. Image credit: NOAA Climate Prediction Center.

Well, the NAO has just flipped back into it's negative phase (Figure 1), and I anticipate that given the five-week periodicity in the oscillation we've been seeing the past few months, we're in for a five-week period of colder than normal weather across most of the U.S. These below-average temperatures should ease up in early March when the NAO flips back into its positive mode. Long range temperature outlooks from the GFS model show the first Arctic air of the year invading the U.S. after Super Sunday, peaking in mid-February. I expect below-zero temperatures will affect most of the Midwest and Northeast by mid-February, with temperatures colder than -20 F in Minnesota. The Siberian Express is on its way!